Cold tube bending apparatus



April 1966 H. J. STEEL 3,243,982

com) TUBE BENDING APPARATUS Filed June 12, 1964 5 Sheets-Sheet l lllllllllllllllllllllllllll I] INVENTOR. Homse J. 57:55;

: T'TOEIVE Y5 April 5, 1966 H. J. STEEL COLD TUBE BENDING APPARATUS 3 Sheets-Sheet 2 Filed June 12, 1964 INVENTOR. Hamse J 57-551- Ax-M, A F 1,16 1 Z A T TOENE Y5 April 1966 H. J. STEEL 3,243,982

GOLD TUBE BENDING APPARATUS Filed June 12, 1964 3 Sheets-Sheet 5 T INVENTOR E 10 HOME? J. 572-54 A T TOENE Y5 United States Patent 3,243,982 CGLD TUBE BENDING APPARATUS Homer 3. Steel, 925 Madera Circle, Box 3%, Elm Grove, Wis. Filed dune 12, 1964, Ser. No. 374,688 Claims. (Ci. 72-150) This invention relates to improvements in devices for cold forming lengths of pipe or tubing into bends or elbows for joining parts of piping systems, and is an improvement on my application S.N. 157,520, filed December 6, 1961, now abandoned in favor of a continuation application S.N. 463,415, filed April 26, 1965.

Generally accepted specifications relating to pipe bends give allowable deviations in Wall thicknesses, inside diameter, outside diameter and the like which are important in the making of bends or elbows. In ordinary bending of pipe or tubing the outer bend wall is stretched while the inner bend wall is shortened. Hence there is a tendency for the outer bend wall to become thinner while the inner bend wall thickens, both of which effects should be minimized.

The broad concept of the present invention accomplishes a short radius bend in which the outer bend wall thickness is maintained practically unchanged, while the inner bend wall thickens only slightly at the mid-portion of the bend. The wall thickness at each end of the bend remains practically unchanged and uniform at all points, while true roundness is maintained. The control of wall thickness is such that pipe of a given nominal size may be used to produce elbows of the same nominal pipe size, and which adequately meet the standard tolerances observed in the industry. The general contour of the elbows is smooth, and the outside wall surface especially is unmarred. The bends can be produced at a rapid rate, which makes the operation an economical manufacturing method. The above advantageous results have been obtained in common steel, stainless steel, aluminum, and in brass materials.

Generally, the present invention provides a device for cold forming of elbows from tubular blanks by pressing pipe lengths on a rotary former under the action of two mandrels inside the workpiece during the entire forming action, with the mandrels moving relative to the axis of the rotary holder and holding the workpiece to the rotary former for a limited arc of movement. A leading mandrel acts inside the forward end of the piece and a pressing mandrel acts inside the trailing end of the workpiece. The mandrel sub-assemblies each include a sleeve which, in the pressing mandrel provides pressure for movement of the workpiece around the rotary former and in the leading mandrel provides a yielding resistance to workpiece movement around the rotary former. Both mandrels have curved surfaces, one part of the surface being substantially cylindrical while another part of the surface is shaped on compound curves, the cylindrical surfaces thereof forming the workpiece into the rotary former groove to form the inner bend wall. But only the leading mandrel acts to form the outer bend wall as the workpiece moves around the rotary former.

In accordance with the invention, the leading mandrel extends into the workpiece for approximately one-half of the length of the piece and moves with the workpiece in an are as it is moved axially in and with the rotary former groove, while the pressing mandrel extends into the workpiece for less than half of the axial length of the workpiece and moves only in a straight line. The two mandrels have similar cylindrical surface portions to cooperate with a uniform peripheral groove in the rotary former for shaping the inner bend wall. The leading mandrel is mounted on the rotary former and moves with it against yielding resistance provided by power means 3,243,982 Patented Apr. 5, 1966 acting on both the rotary former and the leading mandrel. The leading mandrel mounting is grooved for entry of the nose of a stripper as the leading mandrel passes a given point where the leading mandrel sleeve is spaced from the mandrel. The stripper is actuated by the rotary former in a sequence related to rotary former movement and holds the end of the workpiece as the leading mandrel withdraws therefrom.

The rotary former and the mandrel sub-assemblies are each dimensioned to a piece of given diameter and are shaped to maintain the uniformity of diameter required at different cross sections of the workpiece. For a workpiece of l-inch standard weight pipe, tapered leading end of the workpiece is cut to 25 /2 degrees with the maximum length line on the outer bend outer surface and the tapered trailing end is cut to 43 /2 degrees with such line. For a 1" nominal piece to make ells, the approximate length on the outer bend outer surface is four inches. There is a d'nference in length between the outer and inner bend surface lengths of A3" and 1%" respectively at the leading and trailing ends of the piece. An elbow produced from the above workpiece allows trimming of approximately A1" at the ends which provides finished end surfaces well inside the ends of the piece as formed, and removal of metal which has been distorted by flowing between the mandrel and the sleeves which are in only partial contact with the ends of the workpiece.

Referring to the drawings:

FIG. 1 is a perspective view of my present machine for cold forming bends and elbows from piping.

FIG. 2 is a top plan view on the plane 2-2 of FIG. 1.

FIG. 3 is a side elevation of the right hand side of the structure shown in FIG. 1.

FIG. 4 is a partial cross section taken on the plane 44 of FIG. 2.

FIG. 5 is an enlarged cross section of a piece in place for beginning pressing thereon.

FIG. 6 is a cross section taken on plane line 66 of FIG. 5.

FIG. 7 is a cross section taken on plane of line 77 of FIG. 5.

FIG. 8 is a diagram showing the relative positions of a piece at the beginning of the forming stroke, and the position of the stripper and its cam at such time,

FIG. 9 is a diagram similar to FIG. 8 but showing the parts in position when the piece is formed and the strip per is about to engage the workpiece.

FIG. 10 is a diagram similar to FIG. 9 but showing the iece completed, with the pressing mandrel retracted and the stripper engaged to hold and remove the piece from the leading mandrel as the leading mandrel rotates farther with the rotary former.

FiG. 11 is a side elevation of a piece prior to placing the same in the machine.

FIG. 12 is a side elevation of a formed piece after it has been discharged from the machine, and

FIG, 13 is a side elevation of a piece after it has been trimmed and the ends have been bevelled for welding to piping.

Referring specifically to the drawings, numeral 15 represents the bed of any known press of adequate size for the purpose (10,080 p.s.i. or more) and numeral 16 represents the ram of the press, between which are placed a base plate 17 with cylindrical posts 18 at each of three corners, and a top plate 19 with square posts at each of three corners corresponding to the cylindrical posts 18, the square posts having passages therein for slidably receiving the cylindrical posts. The base plate 17, 13 and top plate 19, 29 resemble parts of a press die set which is adapted to receive and position a forming fixture actuated in part by the usual press ram.

thereof.

A pair of heavy pedestals 25, 26 rests on the base plate 17 and each pedestal has a horizontally extending aperture for receiving anti-friction bearings (not shown) in which are journalled the ends of a rotary former 27. The rotary former is roller-like in configuration and has a peripheral groove 28 between the pedestals, of a size dependent on the size of the pieces to be formed. A pair of grooves is formed in the facing surfaces of the pedestals 25, 26 and are spacedfrom the outer periphery of the rotary former 27, and receive a backing plate 34 on which is supported a sliding holder 35 for the pressing mandrel 36,

.42, 43. The holder 35 is formed with outer shoulder portions 37 extending over the rotary former groove 28 with clearance relative to the rotary former, and has a groove portion 38 complementing and facing but spaced from the groove 28. The grooved portion 38 of the holder coacts with the arcuate groove portion 28 in the rotary former in defining an aperture through which the workpiece is pressed. The pressing mandrel 36, 42, 43 extends through a passage in the holder 35 and has a nose end 42 (to be described below) extending in the holder groove 38.

A pair of brackets 45 are severally formed on or fixed to the bearing pedestal 26, one bracket providing a support for a stationary guide 46 which extends over the upper portion of the rotary former groove 28 and which has a nose 47 with an arcuate notch which coacts with groove 28 in providing several areas of support for a wall portion of a workpiece, which areas coact with part of the holder groove 38 so that the workpiece may be supported by at least three spaced points. Guide 46 may be formed integral with such bracket if desired.

A leading mandrel sub-assembly is removably mounted on and moves with the rotary former 27. Such sub-assembly includes rings 50 mounted on the rotary former as by screws 51, and a block 52 secured to the rings and having a passage therethrough for adjustable mounting therein of a mandrel 53 and a sleeve 54 about the mandrel. Block 52 has a groove 55 through which a stripper 59 swings to engage the workpiece after complete forming Thus the leading mandrel sub-assembly is moved with the rotary former, and power means, to be described, provides a yielding resistance as the pressing mandrel sub-assembly causes axial movement of the workpiece around the rotary former.

A shaft 55 is rotatably mounted in brackets 45 and has adjustably fixed thereto a stripper 59 with a nose 6% for engaging the workpiece as the stripper moves through groove 55 in mandrel block 52. A cam follower 61 with a cam roller 62 is mounted on the other end of the shaft 58 and is under the action of a tension spring 63 to engage a cam 64 mounted onan end portion of the rotary former 27, such end portion also bearing a gear 65. Gear 65 engages a rackfi reciprocated by an air cylinder 67 under the control of valve 68. Stripper 59 is mounted on shaft 53 and moves simultaneously with the movement of the leading mandrel and, at a particular time in the forming cycle, engages'and holds stationary an end of the workpiece as the leading mandrel is withdrawn therefrom by the air cylinder.

The pressing mandrel and the leading mandrel sub-assemblies (see FIGS. 5, 6 and 7) each have substantially cylindrical inner curved surfaces so that each of the mandrels coacts with the rotary former groove in shaping the inner bend wall. Each of such mandrels also has a noncylindrical outer surface portion, the leading mandrel outer surface portion being a compound curve to form the outer bend wall of the workpiece. The pressing mandrel sleeve 43 is cut away or relieved on the inner side toward the inner bend wall to allow space for flow of material, and on the outer side is cut into several right angle outwardly facing tooth-like steps across approximately onefifth of the end thereof for more secure seating against the tapered end of the workpiece, The leading mandrel d sleeve 54 is formed with a few relatively large right angle steps and corners facing the outer bend wall, and such sleeve is also relieved at the inner bend wall to allow for some metal flow into the space formed by such relief. The leading sleeve thus concentrates its pressure over approximately two-thirds of the end of the piece from the outer bend wall. 'Howeven-this sleeve can be made similar to upper sleeve 43 when stripperlgroove design permits. FIGS. 6 and 7 show the original axis of the mandrels at points K and L but compound curvature of mandrel outer surfaces shifts the axisto the inner section as indicated by lines MN and XY and such shift is greater as the points of the mandrels are approached,

Reference to FIG. 4 shows that both the pressing and leading mandrel sleeves do not bear on the workpiece end for substantial distances from the inner bend Wall toward the outer bend wall. The pressing holder groove 38 is relieved at its lower end opposite groove 38 to improve the bending contour of outer fibers of the ell. Thus, during forming the outer wall of the workpiece may bend beyond its final point and then spring back. It has been found that this prevents a flat spot in the trailing end portion of the workpiece. FIG. 5 shows that compound curved portions of leading mandrel .53 do not initially bear on the outer bend walls .but bear on such walls with a rolling action without scoring the workpiece, as the parts are moved as indicated vin FIGS. 8 through 10. The leading mandrel surfaces for forming the outer bend walls curve in two directions and act in the workpiece to the extent shown in FIGS. 9 and 10.

FIG. 8 shows the mechanism with the top plate raised and parts cut away to show the relationship of twomandrels, the stripper 59 being retracted as cam follower roller 62 is at that time on slope A of the cam 64. A workpiece a of the size to fit into the passage formed by groove 28, groove 38 and the notch in stationary guide 47, is placed on the leading mandrel to bring the inner bend wall in cont-act with the rotary former groove 28 and into contact with the stationary guide 46. The press is now activated to bring the steps of sleeve 43 into contact with the trailing tip of the workpiece as shown in FIG. 8. The workpiece rests on leading mandrel sleeve 54 and extends over mandrel 53. Leading mandrel'subassembly 50-55 is then ready to yieldingly resist pressure as it moves with rotary former 27, 28.

FIG. 9 shows the pressing mandrel sub-assembly 36, 42, 43 at the end of its stroke while the leading mandrel sub-assembly 50-54 has swung around with thejrotary former 27 by more than Cam 64 has swung to bring cam follower roller 62 about midway of the cam slope B allowing the nose of stripper 59 to approach theentrance of the groove 55. At this moment, valve 68 is operated to reverse the pressure action of air cylinder 67, and separate controls are utilized to cause the press 1am to start upward. The pressing mandrel sub-assembly 36, 42, 43 is thus withdrawn from the end of the workpiece and rises to the top of its stroke.

Actuation of value 68 in a manner desoribed above causes rack 66'and gear 65 to turn rotary former 27 together with cam 64 which allows the follower roller 62 to complete its drop to slope C on the cam-and allow the nose 60 of stripper 59 to move through the groove 55 into the position shown in FIG. 10 where the stripper nose 60 engages the leading end of the workpiece after the leading sleeve has moved away from the workpiece- At that time the stripper is in a toggle position with re-- spect to its fulcrum shaft 58 and holds the workpiece stationary. Continued rotation of rotary former 27 pulls mandrel sub-assembly 5054 from the workpiece,

allowing the workpiece to drop onto plate. 17, whence discharge may be accomplished by any means not shown. Use of an inclined metal chute placed upon the base surface 17, would allow the formed and stripped ell to be discharged to the rear by gravity. Then valve 68'is operated for reversing the air cylinder 67 so that it acts in the forward direction, and by means of rack 66 and gear 65 and rotary former 27 the leading mandrel subassembly 5054 is returned to the position shown in FIG. 4 ready for the next cycle.

FIGS. 11, 12 and 13 respectively show the piece 75a as received by the machine, the piece 75b immediately after discharge from the machine and the piece 750 after it has been trimmed and its end edges bevelled. Both ends of the piece are indented by the ends of the sleeve acting thereon and the metal has flowed, so that the ends are no longer in a plane. However, after the piece is trimmed, measurement of wall thickness all around the ends are found to be well within tolerance. The thickness of the outer wall of the bend is found to be well within accepted tolerances. Roundness of the ends of the finished piece is such as to permit easy welding to piping, and all other features of the usual specifications are satisfied.

I claim:

1. In a machine for cold forming a pipe workpiece into a pipe bend, a rotary former having an arcuate peripheral groove therein, a pressing mandrel sub-assembly having a portion insertable into and a portion pressing endwise on the worpiece and movable in a straight line while holding the workpiece in the rotary former groove, a leading mandrel sub-assembly having a portion insertable into and a portion pressing endwise on the workpiece and movable in an are for holding the workpiece in the rotary former groove, power means for yieldingly resisting movement of the rotary former in one direction and turning the rotary former in the other direction, and a stationary guide coacting with the groove in the rotary former for aligning the workpiece for engagement by the mandrel sub-assemblies.

2. In a machine for cold forming a pipe workpiece into a pipe bend, pedestal parts in spaced relation and having aligned holes, a cylindrical former rotatably mounted in the pedestal holes and having an arcuate peripheral groove therein, a holder slidab-ly supported by the pedestal parts and having a groove therein for receiving a workpiece, a pressing mandrel sub-assembly supported on the holder for insertion into and endwise engagement with the workpiece, the holder and pressing mandrel sub-assembly moving in a straight line only, a leading mandrel sub-assembly mounted on the rotary former and moving therewith in an are about the axis of the rotary former, for insertion into and endwise engagement with the workpiece, power means for resisting movement of the rotary former in one direction and moving the rotary former in return direction, and a stationary guide coacting with and extending along the rotary former and having a notch therein for aiding in supporting the workpiece on the same side as the rotary former, the rotary former and the holder groove and the guide notch coacting in supporting the workpiece on two sides upon entry thereinto and engagement thereof by the mandrel sub-assemblies.

3. In a machine for cold forming a pipe workpiece into a pipe bend, a cylindrical rotary former having an arcuate peripheral groove therein, a pressing mandrel sub-assembly having a portion insertable into and a portion pressing endwise on the workpiece and movable in a straight line while holding the workpiece in the rotary former groove, a leading mandrel sub-assembly having a portion insertable into and a portion pressing endwise on the workpiece and movable in an are about the rotary former axis for holding the workpiece in the rotary former groove, both the inserted mandrel portions remaining in and moving with the workpiece during forming thereof, power means for yieldingly resisting movement of the rotary former and the leading mandrel during forming action and returning the same to an initial position after the formed workpiece is removed, and means operabie by the rotary former for engaging an end of the workpiece to strip the workpiece off the leading mandrel upon completion of the forming action.

4. The device of claim 3 in which a cam on the rotary former actuates a cam follower mounted on a shaft to swing a stripper on the shaft into endwise engagement with the workpiece for stripping the workpiece ofi the leading mandrel after movement thereof to intersection of the workpiece end with the arc of movement of the stripper.

5. In a machine for cold forming a pipe workpiece into a pipe bend, a rotary former having an arcuate peripheral groove therein, a pressing mandrel sub-assembly having a portion insertable into and a portion pressing endwise on the workpiece and movable in a straight line while holding the workpiece in the rotary former groove, a holder for movement with and relative to the pressing mandrel and grooved to receive the workpiece, a leading mandrel sub-assembly having a portion insertable into and a portion pressing endwise on the workpiece and movable in an arc for holding the workpiece in the rotary former groove, and power means for yieldingly resisting movement of the rotary former in one direction and turning the rotary former in the other direction, said holder groove being relieved for a part of its length and a stationary guide is positioned to support the workpiece only until the relieved portion of the holder groove has passed beyond the end of the stationary guide.

References Cited by the Examiner UNITED STATES PATENTS 2,357,006 8/1944 Johnson 72159 2,971,556 2/1961 Armstrong et al 7242 FOREIGN PATENTS 461,988 7/ 1928 Germ-any.

References Cited by the Appiicant UNITED STATES PATENTS 1,903,436 4/1933 Brown. 1,978,452 10/1934 Flodin.

1,993,361 3/1935 Cornell. 2,002,470 5/ 1935 Cornell. 2,221,417 11/ 1940 Taylor. 2,335,342 11/ 1943 Kvarnstrom. 2,583,404 1/1952 Wyrfel. 2,907,102 10/ 1959 Armstrong et al. 2,918,102 12/1959 Klein.

3,110,341 11/1963 Stalter.

CHARLES W. LANHAM, Primary Examiner.

R. D. GREFE, Assistant Examiner. 

1. IN A MACHINE FOR COLD FORMING A PIPE WORKPIECE INTO A PIPE BEND, A ROTARY FORMER HAVING AN ARCUATE PERIPHERAL GROOVE THEREIN, A PRESSING MANDREL SUB-ASSEMBLY HAVING A PORTION INSERTABLE INTO A PORTION PRESSING ENDWISE ON THE WORKPIECE AND MOVABLE IN A STRAIGHT LINE WHILE HOLDING THE WORKPIECE IN THE ROTARY FORMER GROOVE, A LEADING MANDREL SUB-ASSEMBLY HAVING A PORTION INSERTABLE INTO AND A PORTION PRESSING ENDWISE ON THE WORKPIECE AND MOVABLE IN AN ARC FOR HOLDING THE WORKPIECE IN THE 